the city has identified thousands of buildings which need the retrofitting. and the upgrades would run property owners thousands of dollars. kron-4's alecia reid is in san francisco with more. >> reporter: this will be one of the buildings proposed by the supposed regulations. this recommended mandate is targeting this building that is known to be vulnerable. wood frame buildings with three or more stories. with also, if there were built before the year, 1978. these buildings could be week with a garage on the fourth floor or and open construction spot like this. the 1989 threat earthquake is very real. retrofitting is essentials. >> from the foundation, down. the probability of a larger required, 7-8 magnitude in the next 30 years is greater than 30%. we are looking at very significant statistics >> reporter: 3000-4000 homes are in danger. the entire city would be impacted. >> not only to the risk of an owner, a risk to the entire buildings. the entire housing market, workforce and entire workforce and city recover quickly could be impacted >> reporter: this